Couldn't wait for the upswept muffler, and like the straight look better anyway, so I put a shorty muffler on my new C5 this weekend, just like the one in the photo at the first of this thread. Thought I’d pass on some experiences in case this makes it go more easily for the next guy. It was actually pretty easy for this non-mechanic and the look and sound is well worth it in my opinion.

First step, at least for those of you in the U.S., call Classic Motorworks. You want CMW Item #Z90373, “RE Classis Silencer Short 500 #4”. And while I know r80rt used a Drag Specialties heat shield to hide the joint between the head pipe and muffler, I’d stay on the phone long enough to order Item #Z91403, “Exhaust Heat Shield, Woodsman.” It’s the right size, you get one-stop shopping, and it comes with a couple very handy clamps as noted below.

I had two challenges during the install. One is that the hanger bracket supplied with the muffler doesn’t hang it straight on the C5. Luckily it is made of fairly soft metal. If you loosely install the frontmost bolt on the muffler and the nut on the footpeg that serves as the top hanger bolt, and straighten the muffler by hand, you will see that the rearmost bolt on the muffler really needs a hole about ½” above the one cut into the bracket. I marked that position with a Sharpie, drilled a small pilot hole in the bracket, then enlarged it with a larger bit to about 5/16” to 3/8” (precision not needed, it’s not visible when installed), and the muffler came into perfect alignment with the headpipe.

Second challenge: the inner diameter of the muffler is slightly larger than the outer diameter of the headpipe, so you don’t get a snug fit, and the cinch bolt on the muffler won’t compensate for this. At the same time, the exterior diameter of the muffler is too large for the clamps that come with the heat shield to hold it in place (but they are just the right size for the headpipe). I found an easy fix. First, get about a 2” conventional clamp from a hardware or auto parts store or a neighbor’s car radiator to hold the heat shield on the muffler end. Then cut one of the fancy Enfield heat-shield brackets right at the point it’s connected to the worm screw apparatus (I used the “squeeze with diagonal cutters, grunt, and then bend back and forth at the unsuccessful cut-line” approach). You now have a shim pretty much exactly the size and diameter you need to seal between the header and muffler. Place the Enfield shim you didn’t cut apart, around the header pipe just behind the standoff mount that was used for the old muffler’s heat shield and secure it, that gives you something to push against. Then place the new shim around the headpipe, work it into the opening of the muffler, and smoosh the two together. Should end up tight enough that even without the bracket, the pipe is tight and the muffler supports itself.

Remove the “good” Enfield bracket from the headpipe and place it in front of the old standoff mount, where it will then serve its intended purpose of holding the new heat shield in proper position. Insert all nuts/bolts in the hanger bracket you drilled out in step #1 and tighten. Tighten the clamp that’s incorporated into the front of the muffler. Install the new heat shield using the Enfield clamp in front, and the larger hardware-store clamp in back, and clip off the extra part of the hardware-store clamp. Admire your work. Start the bike and grin. Slightly louder, much throatier, much more attractive and classic-looking. Stow the old muffler against the possibility you have to pass some emissions test and need the catalyst feature to do that, because this installation is easily reversible.